The present invention relates to devices comprising an electronic energy converter which, fed from an AC distribution mains, may provide at its output a high frequency current whose readily adaptable potential is applicable to a majority of receivers, either directly or after previous rectification.
Known devices of this kind are numerous and could be classed in the two following types :
the first one, illustrated in the accompanying FIG. 1, comprises a high frequency converter 5 whose DC input is shunted by the electrolytic smoothing capacitor 4, which is charged by the mains rectifier bridge 3 whose AC input is connected to the mains terminals 1a and 1b through the low pass filter 2 characterized by its considerable ferromagnetic inductance associated with capacities of values which are often high:the purpose of this filter is to limit the harmonic currents caused by charging of the smoothing capacitor 4 to the peak voltage of the mains, as well as to bring the shape factor of the current taken from the mains and the power factor of the device down to standardized values, whereby the voltage present between the input terminals of the converter 5 only has low residual modulation, which thus results in the fact that between its output terminals 6a and 6b the envelope of the high frequency AC voltage is only weakly modulated by the low frequency component of the rectified mains, thus lending itself to numerous applications, with or without rectification of the high frequency current; PA1 the second one, illustrated in the accompanying FIG. 2, still comprises a converter 5 but the input thereof is now only shunted by a decoupling capacitor 6 for the high frequencies, which capacitor has a sufficiently small capacity for charging thereof by the mains rectifier bridge 3 not to create substantially harmonic currents on the current taken from the mains; thus, the voltage applied to converter 5, not being filtered by a high value capacitor, is modulated in accordance with the amplitude of the sinusoid of the mains, which results in equivalent modulation of the high frequency output current delivered by said converter; such a voltage envelope is satisfactory for few applications and thus, in most cases, it is necessary to rectify the high frequency current by means of the rectifier bridge 7 whose output current is filtered by the high value electrolytic capacitor 8, thus permitting a load applied between terminals 9a and 9b to be fed with substantially DC voltage.
Other devices have been envisaged, namely, the use of a complementary converter for charging said capacitor 4 with a good shape factor of the current taken from the mains, without having recourse to the bulky anti-harmonic filter 2.
Such devices have serious drawbacks, which are enumerated below.
In devices of the first type, which are the most widespread, filter 2, which is cumbersome and heavy, by its own losses greatly reduces the electric efficiency of the unit while providing a suitable function only over a very reduced input voltage and frequency range; furthermore, for numerous applications, the long term reliability of the electrolytic capacitor 4 is unacceptable; this therefore restricts their field of application.
In devices of the second type, the supply current for converter 5, which is highly modulated, limits the electric efficiency which this latter might offer; moreover, the very high modulation of its high frequency output current renders it suitable for only a small number of applications if previous rectification is not provided by means of bridge 7 and filtering by means of the electrolytic capacitor 8 of a special and expensive type. Thus, with devices of this type a high frequency current only weakly modulated by the mains component cannot be delivered, which represents the majority of potential uses.
In so far as the devices using an auxiliary converter are concerned, the complexity of construction, the increase of high frequency parasite signals, control of the operation of the auxiliary converter and electric efficiency losses which it causes, have never made it possible to develop them industrially in a significant way.
Contrary to the known devices of the prior art, described above, the device of the invention completely overcomes all the above drawbacks, while only using a device of simple, economic and reliable construction.